Interim data show 2019-20 flu vaccine reduced doctor visit risk by 45% overall, 55% in childrenHow well did this year's flu shot work? Early data shows protection, especially for kids

An interim observational report provided preliminary estimates of 2019-20 seasonal influenza vaccine effectiveness in the United States, with a focus on children. The analysis examined the association between vaccination and the risk of having to visit a doctor for influenza illness. No comparator group details, sample size, or follow-up duration were reported.

The main finding was an estimated 45% reduction in the risk of a doctor visit for influenza illness in the overall population. For children specifically, the estimated risk reduction was 55%. The report did not provide absolute numbers, p-values, or confidence intervals for these percentage estimates, limiting assessment of their precision.

Safety and tolerability data were not reported. The authors explicitly noted these findings represent associations, not proven causation, and are preliminary interim estimates. Key limitations include the observational design and lack of reported data on generalizability beyond the specific season and population. For practice, these early estimates suggest a protective signal but require confirmation with final, more complete data.